Agitator



H. J. SMITH AGI TAT OR Filed Deo. 8, 1927 4 Sheets-Sheet l Oct. '29, 1929. H. J. SMITH 1,733,244

AGITATOR Filed Dec. B. 1927 4 Sheets-Sheet 2 oct., 29, 1929. H. J. SMITH 2,733,244

AG I TATOR Filed. Dec, 8, 1927 4 Sheets-Sheet 3 Oct. 29, 1929.

H. J. SMITH AGITATOR Filed Dec. 8, 1927 4 Sheets-Sheet 4 oa. as, reza 'nanna a". satira, or aannwoon, @nro AGTATR application inea neeember e, rear.

'lhis invention relates to an agitator which is more particularly designed tor mixing liquids such as paint, paper pulp, cement, slurry, chemicals, and the like, and which depends for its operation on the principle of the Venturi tube.

.agitation of liquids for mixing them in a tank has heretofore been more or less haphazard, inecient and unsatisfactory. Production of turbulence in the liquid by Inechanical stirring has been a fundamental method ci mixing the same. But usually such stirring is only of a local nature and a real mixture of the entire mass is rarely, i ever, attained. The same condition results from the use of air introduced under pressure into the liquid and passing through the same in the form of bubbles, no homogeneous ymixing or the liquid being possible.

rlhe object of this invention is they provision of an agitator whereby the entire mass of liquid will be mixed thoroughly, homogeneously and quickly with a minimum ex penditure of power.

To that end this invention contemplates to use a Venturi tube in its` organization in which a distinct circulation of the entire volume of liquid is obtained and all parts of the same are intimately mixed.

ln the accompanying drawings:

Figure 1 is a verticalsection of one form of Venturi tube agitator embodying my invention. Figure 2 is a top plan view thereof. Figures 3 and 4' are horizontal sections taken on the correspondingly numbered lines in Fig. 1. Figure '5 isa fragmentary vertical section taken on line 5 5, Fig. 2. Figure 6 is a fragmentary side elevation of the means for raising and'lowering the vertically movable part of the Venturi tube shown in Fig. 1. Figure 7 is a vertical section of another form of my improvement. Figure 8 is a horizontal section taken on line 8 8, Fig. 7. Figure 9 is a :fragmentary vertical section of the lower part ofthe tank and the Venturi tube showing another modification of my invention. Figures 10, 11,12 and 13 are diagrammatic views in vertical section, side elevation, top plan and bottom plan showing the action or the liquid currents during the opsenai no. aeaeea eration of my improved agitator. Figure 1li is a vertical longitudinal section of a orm of apparatus embodying my invention in which the Venturi tube is arranged horizontally.

ln the following description similar characters oi" reference indicate like parts in the several iigures of the drawings.

Referring to Figs. 1 6, the numeral 2O represents an upright tank which is adapted to hold the charge of liquid to be mixed and which may be constructed o any material to suit the character of the liquid under treatment. rThe liquid may be introduced into the top of the tank at the top and withdrawn from the bottom thereor" through a pipe 2l having a suitable valve for controlling the same.

rllhe means whereby the mixing of the liquid is effected in accordance with my in vention are constructed as follows:

Arranged vertically within the central part of the tank is a Venturi tube which has a reduced or contracted throat 22 between its upper end lower extremities, an upper conical section 23 which is comparatively long and tapers downwardly toward the throat and a lower conical section 24 which is comparatively short and flares downwardly from the throat and terminates at a distance from the bottom of the tank so Aas to form a lateral passage 25 between the lower end of the Venturi tube whereby communication is established'between the interior of this tube at the lower end thereof andthe annular space 26 intervening between the exterior of this tube and the wall of lthe tank.

In the preferred construction a base 27 rests on the botton'ro the vtank below the tube and is connected with the lower section of the same by a plurality of posts 28 arranged in an annular row, said lower tube section, base and postsbeing preferably cast in one piece of metal. The upper conical section is preferably made up of a vertical series of progressively larger conical elements 29 which are constructed of sheet metal Yand separated from one another by annular slots or circumferential openings 30, and a plurality of upright bars 31 of angle iron secured to the outer side of the several elements so as to'connect them and hold them in Venturi tube the upper section is divided along` the transverse line 3-3 forming a lower fixed part 32 and an upper movable part 33 which is adapted to normally resti on the lower part 32 but can be raised to form a gap between the lower and upper parts. 33, 32 through which liquid can pass for the purpose of continuing the` mixing operation while emptying the mixing apparatus as will be more fully explained later on. The lower part 32 of the upper cone section of the Venturi tube is preferably cast integrally wlth the lower cone section, as shown in `ig. 1. The upper and lower cone sections 23 and 24 of the tube are retained in their proper relative position and the upper section is guided in its movements toward and from the loWerj section by` guiding and retaining means consisting preferably of a plurality f upright guide pins 34 projecting upwardly from the lower tube section 24 on the exterior thereof and guide eyes 35arranged on the exterior of the lowermost sheet metal unit of the upper tube section and each receiving the up er end of one of said in igs. 1 and 3.

The numeral 36 represents a propeller whereby the liquid to be mixed is circulated through the Venturi tube and the tank, which propeller is arranged. within the Venturi tube and preferablyin line with the throat thereof and turned in the direction for causing the liquid to flow downwardly on the inner side of the tube and upwardly between the outer side of the tube and the tank. In the construction shown in Fig. l the base 27 is provided with an upwardly coned or dished central part 37 which carries an upwardly projecting pivot pin 38 on which the lower end of the hub of the propeller is jour-v naled. Arranged centrally within the Venturi tube is an upright stirring shaft 40 which is secured at its lower end to the upper end of the hub of the propeller while 'the upper part oi. the shaft is jour aled above this tube in a bearing 41 mounted on a cross piece 42 carried by means 43 on the upper end of the tank. Upward motion of the stirring shaft is prevented by a thrust collar 48 secured to this shaft and engaging with the lower end of the upper bearing 41, as shown'in Fig. 1. Rotation of this shaft together with the propeller mounted thereon may be eiected in various ways, for example by the means shown in the drawings consisting of a lhorizontal driving shaft 19 journaled in bearings 44 on the cross piece and receiving power from any suitable source, a bevel gear pinion 45 mounted on the driving shaft and meshing with a bevel gear wheel 46 secured to the upper 'end of the stirring shaft, and a guide pins, as shown clutch 47 for connecting and disconnecting the driving shaft and driving bevel pinion.

Raising and lowering of the upper part of the Venturi tube for opening or closing a gap or passage between the same and the lower part of the tube immediately above the throat and propeller may be accomplished by a variety of means but those shown in Figs. l, 2, 5 and 6 are satisfactory and constructed as follows:

The numeral 49 represents an uprighty 'raised and lowered. Along the side ofthe stirring shaft and guide sleeve is arranged a horizontal hoisting or lifting shaft 52 which is journaled in suitable bearings 53 on the beams and adapted to be turned manually by a gear segment 54 secured to one end of this shaft, a worm 55 meshing with this segment, a hand shaft 56 journaled in bearings 57 on the adjacent beam and carrying the worm, and a handle 58 on said shaft for manipulating the same, as shown in Figs. 2, 5 yand 6. On opposite sides of the stirringshafttwo hoisting drum segments 59 aremounted on the hoisting shaft and to each of these hoisting segments one-end of a hoisting line 60 is secured and adapted to be wound thereon, the opposite end of the respect-ive line being connected to the guide spider 50 at the upper end of the vertically movable part of the Venturi tube. Upon turning the drum segments in one direction or the other the upper part of the Venturi tube will be raised or lowered for a purpose which will presently appear. l

In the modiied form of my invention shown'in Fig. 9 the lower cone 61 of the Venturi tube is made of a steeper angle as compared with the .relatively fiat angleof the lower cone 24 in Fig. 1, and the 'lower end of the stirring shaft 62 is journaled on the pivot pin 38 instead of journaling the hub of the propeller thereonvas in Fig. 1.

In a simplified form of my invention, as shown in Figs. 7 and 8 the upper and lower cones 63, 64 of the Venturi tube may be made more nearly' equal in length with lthe lower somewhat shorter than'the upper, in which case the propeller 65 rotating in the throat 66 wouldbe farther from the bottom of the liquid tank 67. This particular form of my invention also shows the upper and lower vae cones of the Venturi tube immovable relatively to one another.

If desired, the Venturi tube 68 of this form may be mounted horizontally in the tank 69 and ythe propeller 70 may be operated by a horizontal stirring shaft 71 extending to the exterior of the tank, as shown in Fig. 14.

When t-he apparatus is in operation the mixing of the liquid is effected in the manner which is illustrated in the diagrams shown in Figs. 10-13 as follows:

The liquid to be mixed is let into the tank until the later is filledto a level high enough to submerge the Venturi tube and the top of the tank, and the upper part of this tubeisy fully lowered when operating the machine shown in Fig. 1.

Upon now turning the propeller of this form by means of its driving mechanism the liquid is caused to How in a general current which descends in the tube and raises outside of the tube and in this general current thus generated there are regular phases of eddy currents which are constantly in action.

, These eddy currents may be divided into live main phases in which molecular turbulence occurs, these phases being located approximately inthe various places or zones marked A, B, C, D, and E in the diagrammatic Figures 10, l1, 12 and 13. Referring now to these last mentioned gures it has been found that in the zone A at the upper end of the Venturi tube the liquid to be mixed is given velocit bythe action of the screw shaped propel er in the throat of the Venturi tube. In this region or zone the progress of the liquid is from the annular volume between the Venturi tube and the tank and mixes at the top of this tube before entering the same. The molecules converge to the center of the tube from every point of the tank circumference and merge or roll together as they dive into the top of the Venturi tube. i

When the liquid reaches the zone B in the throat of the Venturi tube thepropeller whirls the molecules and forces them downward at a velocity which is variable depending on the diameter of the tube and the speed of the propeller.

As the current of liquid issues from the lower end of the .Venturi tube the same is shot out in sharply defined radial curves in all directions forming phase or zone C at a maximum velocity toward the lower end of the annularpassage between the tube and the wall of the tank. As the current rises in the last mentioned passage the same divides into the phases D, E, of which the phase D curves upwardly along the inner side of the tank wall and spreads its molecules fan-wise into a blend with neighboring currents which stream upwardly in vertical paths, while the series of eddy currents .forming the phase E impinge at high velocity against the large volume of liquid in the tank next to the contracted part of the Venturi tube and thus effects a great but orderly turbulence in this region. The whole volume of liquid is thus set rolling and mixing in this particular Zone so that part of the molecules flow downwardly above the throat of the same moves upwardly in vertical paths and passes radially inwardly from all directions to the phase A preparavtoryto. beginning another cycle in the course of circulating through the agitator.

A laboratory demonstration shows that the current velocity in the case of cement slurry was fixed at thirty feet per minute and excellent mixing is obtainable at even considerably slower rate of motion. If, however, the current is too low it lacks the momentum to start the whole mass promptly through the cycle of phases after a prolonged shutdown.

At this velocity of thirty feet per minute the screw propeller starts and establishes the cycle current in thirty seconds after shutdowns up to sixty-six hours of rest. The

specific gravity of the slurry in the last instance registered 1.80, and the capacity of the tank was ten and one-half gallons.

The consumption of electric current for operating the motor at 230 volts and 1720 R. P. M. for driving the propeller was as follows:

Motor-alone 0.440 amperes Motor and transmission- .680 amperes Motor, transmisison and screw n .715 amperes Used in mixing slurry .034 amperes Used in mixing slurry 8.05 watts for 10% gallons Used in mixing slurry-.. .76 lwatts per gallon -the upper part of the Venturi tube it is possible to keep the propeller fully supplied with liquid even' though the level of the same reaches a very low position. When the level of the liquid is above the top of the Venturi tube most of the upstreaming liquid passes by the annular openings in the Venturi tube and enters the upper or suction funnel of the these openings is in turn uncovered by the liquid. `When the level of the liquid drops below the lowermost aperture, the flow of liquid from the tank through the Venturi tube to the propeller is obtained by raising the f upper part of this tube by the lifting mechavao nism thereby supplying liquid directly to the propeller. `When the level of the liquid sinks below the upper fixed line of thethroat and until the liquid level drops below the lower edge of the propeller, the latter exerts a violent beating action on the liquid whereby the latter is thoroughly agitated and kept in a mixed condition until the tank ispractically empty. During its operation the propeller shoots out an annular ring of liquid with suflleient force to overcome the specific gravity of the heavy materials in the liquid so as yto keep the bottom of the tank clear and not allow any heavy particles to settle there.` The continued pressure of the propeller against the lower end of thecolumn of liquid outside of the' Venturi tube causes this liquid to shoot upwardly in a violent state of turbulence which results in intimately mixing' the ingredients in a minimum length of time, and thus *effects a substantial saving in work of this character.

When constructing the apparatus as shown in Fig. l in which the openings 30 are employed in the upper part of the Venturi tube at different levels thereof, these openings should be made of the proper size so that .normally the bulk of the liquid will pass upwardly on the outside of the tube to the top of the same and only a small quantity will enter this tube through these openings, thereby ensuring the longest path for most of the liquid as it circulates through the machine and thus produces the most ell'ective agitation of the same. Such liquid as may enter the tube through the openings 30 mingles with the descending stream in the tube and setsup addition turbulence which further exped1tes the mixing operation and produces a mixture of uniform consistency in less time than has been possible heretofore.

It will be noted that in Figure 1 the bearing for the lower end of the upright shaft l0 has an external downwardly flaring 'surface which leads from the upper reduced end of this bearing laterally to the openings at the lower end of the mixing tube and that the hub 39 of the propeller which is secured to the shaft also flares downwardly and that the lower edge of this hub overhangs the upper reduced end of the lower bearing.

By these means the propeller when turning for the purpose of forcing vthe current of liquid downwardly will tend to lift t-he driving shaft so that the liquid escaping through these lower openings will produce a suction or straining effect on the slight gap which will be present between the lower bearing of ythe shaft and the hub and thereby permitting only liquid to enter this space but preventing any solid material from entering the same so that wearing of the parts at this point and possible interference with the operation of the apparatus is prevented. This action ot causing asuction `on -the joint between the lower shaft bearing and the hub of the propeller is further increased by the slight overhang of the pro eller hub relative to the upper reduced en of the base portion of the bearing.

I claim as my invention: y

1. An agitator comprising a tank, a double cone Venturi tube arranged within said tank and having an inflow section provided with an opening in its side and an outflow section, and a propeller arranged in said tube below said opening.

2. An agitator comprising an upright tank, a tube arranged within the tank and having an intermediate throat, an upper conical inflow section tapering toward said throat and provided with inflow openings at di'erent points in its height and a lower outflow section which flares downwardly from said throat, and a propeller arranged within the throat of said tube. y

3. An agitator. comprising an upright tank, a Venturi tube arranged in said tank and having an intermediate throat, an upper inflow section tapering downwardly toward said throat and a lower outflow section flaring downwardly from said throat, said tube being divided above said throat and the upper part thereof. above said division being vertically movable, and a propeller arranged in said throat.

4. An agitator comprising an upright tank, a Venturi tubearranged within the tank and havin an intermediate throat, an upper conical inow section tapering toward said throat `and provided with inflow openings at difierent points in its height and a lower outflow section which flares downwardly from said throat, said tube being divided above said' throat and the upper art thereof above said division being vertica l movable, and a propeller arranged in the t roat of the tube.

5. An agitator comprising an upright tank, a Venturi tube arranged 1nsaid tank and having an intermediate throat, an upper inflow section ltapering downwardly toward said throat and a lower outflow section flaring downwardly from said throat, said tube being divided above said throat and the upper part thereof above said divisions being vertically movable, a propeller arranged in said throat, and means for raising-and lowering the upper part of said tube.

6. An agitator comprising an upright tank, a Venturi tube arranged invsaid tank and having an intermediate throat, an upper inflow section tapering downwardly from said throat, and a lower Voutflow section Haring downwardly from said throat, said tube being divided above said throat and the upper part thereof above said division being vertically movable, a propeller arranged in said `throat, and means for raising and lowering the upper part of said tube, including a vertically swinging hoisting segment, and a line connected with the upper part of said tube and adapted to be wound on said hoisting segment.

7 An agitator comprising an upright tank, a Venturi tube arrangedv 1n said tank and having an intermediate throat, an upper 'inflow section tapering downwardly toward said throat, and a lower outflow section flaring downwardly from said throat, said tubo being .divided above said throat and the upper part thereof above said division being ,vertically movable, a propeller arranged in said throat, and means for raising and lowering the upper part of said tube, including a vertically swinging hoisting segment, a line connected with the upper part of said tube and adapted to be wound on said hoisting seg ment, a gear segment operatively connected with said hoisting segment, and a worm meshing with said gearment.

8. An agitator comprising an upright tank, a Venturi tube arranged in said tank and havingvan intermediate throat, an upper inflow section taperingl downwardly toward said throat and a lower outflow section aring downwardly from said throat, said tube being divided above said throat and the upper part thereof above said division beine' vertically movable, a propeller arranged 1n said throat, and means for guiding the upper part of said tube relative to the lower part thereof. 9. An agitator comprising an upright tank, a' Venturi tube arranged 1n said tank and having an intermediate throat, an upper inflow section tapering downwardly toward said throat and a lower outflow section ilaring downwardly from said throat, said tube being divided above said throat and the upper part thereof above said division being vertically movable, a propeller arranged 1n said throat, and means for guiding the upper part of said tube relative to the lower part thereof, including a plurality of guide pins projecting upwardl from said lower part, and a plurality o guide-eyes arranged on the upper part of said tube and receiving said guide pins.

10. An agitator comprising an upright tank, a Venturi tube arranged in said tank and having a contracted throat intermediate of its upper and lower ends, an upper section which tapers downwardly toward said throat and a lower section which 'flares downwardly from said throat, said upper section being provided with a plurality of annular slots arranged at different elevations in the the height of the tube, and a plurality of upright bars secured to said upper section and extending across the slots thereof, and a propeller arranged in said tube.

11. An agitator comprising an upright tank, an upright Venturi tube arran ed within the tank and having a reduced t roat between its'upper and lower ends, an upper section tapering downwardly toward said throat and an upper section flaring downwardly from said throat, said upper section being divided and forming an upper part which is movable vertically, a propeller arranged within the tube, an upright shaft arranged within the tube and carrying said propeller, a lower bearing which is arranged below the tube and on which the propeller is journaled, an upper bearing which is arranged above the tube and in which the upper part of said shaft is journaled, a collar on said shaft and engaging the lower end of said upper bearing` a guide sleeve surrounding the upper part of said shaft and depending from said bearing, a hub arranged on the vertically movable part of said tube and slidable on said guide sleeve, and means for raising and lowering'said upper part of the tube.

12. An agitator comprising a tank, an upright tube arranged within said tank and having open upper and lower ends and having circumferentially extending openings in itsbside, and a propeller arranged within said tu e.

13. An agitator comprising a tank, an upright mixing tube arranged within said tank and having open upper and lower ends, an upwardly tapering conical base arranged at the lower end of said tube and provided centrally on its upper small end with a pivot pin, a propeller arranged in the lower part of said tube and having a downwardly fiaring hub which is journaled on said pin, and an upright shaft arranged in said tube and connected at its lower end with said hub and journaed at its upper end on said tank above said tu e.

14. An agitator comprising a tank, an upright mixing tube arranged within said tank and having open upper and lower ends, an upwardlyY tapering conical base arranged at the lower end of said tube and provided centrally on its upper small end with a pivot pin, a propeller arranged in the lower art of said tube and having a downwardly aring -hub which is journaled on said pin, and an upright shaft arranged in said tube and iso connected at its lower end with said hub and journaled at its upper end on said tank above said tube, the lower end of said hub being of larger diameter and extending laterally 5 eyond the upper small end of said conical ase.

15. An agitator comprising a tank, an upright tube arranged Within said tank and having open upper and lower ends and provided with a plurality of circumferentially extending openin s in its side at different pointsvin the heigt thereof, and a propeller arranged Within the tube.

In testimony whereof I, hereby aHix my signature. 15 HARRY J. SMITH, 

